3. The event-handling method connected to EXPANDED or EXPANDING receives three
arguments: the control ID of the tree view control, the tree item expanded or collapsed, and a
string that indicates whether the item was expanded or collapsed. Example:
::method onExpanding unguarded
use arg id, item, what
say "Item with handle" item "is going to be" what
The example text "is going to be" is confusing and should read "was" (or something along those lines).